Computer controlled techniques for the pattern dyeing of substrates are well known. For example, the following commonly assigned U.S. Pat. No. 4,055,868 (O'Neill, Jr.), U.S. Pat. No. 4,111,012 (Stewart, Jr.), and U.S. Pat. No. 5,208,592 (Johnson, Jr.), all hereby incorporated by reference herein--disclose the patterning of substrates in which a series of arrays are arranged in spaced, parallel relation across the path of a moving substrate web. Each array is comprised of a plurality of individually controlled dye applicators or jets, all of which are supplied with dye of a color that is different and specific for each array. As the substrate passes each of the arrays, the dye applicators of that array are individually actuated by a computer containing stored pattern data. The result is that the various dye applicators in each array apply, via a controlled stream or spray, the liquid dye associated with that array in the quantity and configuration necessary to construct, color by color, the desired pattern as the moving substrate passes each array. Because the dye is not fixed until all patterning is complete, the in situ blending of dyes from different arrays may be controlled to generate, as desired, colors that are mixtures of the colors of the individual dyes.
This patterning technique, while offering many advantages over other patterning techniques in commercial use at this time, nevertheless has been the subject of further development. The results of that development are improvements in the following areas.
Occasionally, while attempting to dye a section of substrate a single, solid color, the above-described technique will generate unwanted streaks or other undesirable shading differences, either across the width of the substrate or along its length. Also, because the range of colors that may be deposited on the substrate is necessarily limited by the number of arrays (and therefore the number of available colors of liquid dye), it is sometimes necessary to change the color of dye in one or more arrays to allow the reproduction of a specified color that cannot be obtained using the combination of available liquid dyes.
This process requires time consuming steps to remove the old dye, thoroughly clean the array so that the old color dye does not contaminate the new color dye, refill the array with the new dye, and resume the dyeing operation. Therefore, any technique that allows for the reproduction of a wider range of colors from a given set of liquid dyes is very desirable if production delays are to be minimized. Furthermore, any technique that allows for an increase in the speed at which the substrate can pass under the arrays, with no adverse effect upon the quality of the resulting pattern, is also very desirable, as it will tend to increase product throughput. The invention disclosed herein offers these advantages, as well as others that will be discussed in, or become apparent from, the following disclosure. The above comments are believed to apply to other similar discrete dye applicator patterning devices. One such device is described in commonly assigned U.S. Pat. No. 4,923,743 to Stewart, Jr., which is hereby also incorporated by reference.
The instant invention combines the advantages of computer-controlled patterning, as described above, with known textile dyeing techniques in which a heated liquid dye of a single color is applied to a substrate in a way that allows the dye to become fixed in the substrate without the need for any additional steaming or other fixation step. Such a technique is described generally in, for example, U.S. Pat. No. 4,790,043 to Chappell and U.S. Pat. No. 4,578,836 to Otting, et al. This single step dyeing technique is used herein in connection with the uniform application of a single light, neutral shade to the substrate to be patterned. As so used, this or similar single step dyeing techniques in which the dye is fixed on contact shall be referred to generically herein as the solid shade dyeing technique, and the specific apparatus used to implement this technique shall be referred to as the solid shade dyer.
In the instant invention, the solid shade dyeing technique described above is used before any patterning of the substrate takes place. In this process the carpet is dyed a solid, relatively neutral shade (e.g., a light beige) in a way that makes unnecessary a separate dye fixation step for the solid shade. This is achieved by applying hot dye in a way that prevents the dye from cooling before it strikes the substrate surface. By using heated dye and applying it in an environment in which cooling effects such as evaporative cooling, heat dissipation in the substrate, etc. may be minimized, the uniformly applied dye can fix to the substrate on contact, without the need for subsequent steaming or other conventional fixing techniques.
Unexpected advantages have been observed when these two technologies are combined. By applying the patterning dye to a substrate to which dye has already been uniformly applied and fixed, the quantity of dye needed to pattern the substrate is appreciably reduced, thereby reducing dye costs and allowing the substrate to be moved much more rapidly past the patterning arrays and dramatically increasing the throughput of the machine. Perhaps more importantly, the dyed quality of the patterned areas is improved--the dyed areas are dyed more uniformly, with cleaner interfaces between adjacent dyed areas, when compared with patterned substrates that were not previously subject to the solid shade dyeing step described above.
Yet an additional advantage is that this development makes possible the practical manufacture of carpet tile starting with broadloom carpet. Ordinarily, the normally insignificant side-to-side or side-center-side shade differences associated with dye jet patterning of the kind described above precludes cutting carpet tiles from broadloom carpet because of the need for extensive sorting of carpet tiles at the time of packaging or installation. This sorting step has been found necessary to prevent gradual shifts in shade that might occur in the course of a given production run--and that might be imperceptible if viewed over a relatively large expanse of broadloom carpet--from being emphasized through the chance side-by-side placement of tiles, cut from widely separated areas of the broadloom carpet, that reflect the extremes of the shade shift that occurred within that production run. Thus, to assure reasonable tile-to-tile shade uniformity at the time of installation, generally it has not been commercially practical to use broadloom to generate carpet tiles. This invention removes this obstacle.
The reasons for these unexpected advantages are not yet fully understood. It is known, however, that treating the substrate with steam or water (with or without surfactants) prior to pattern dyeing does not yield the same improvement, so it is not merely the effects of a moist or heated substrate. It is conjectured that the fibers comprising the substrate are bulked in a consistent way, with uniform moisture imparted to the fibers, thereby resulting in a more dependably uniform receiving surface for the patterning dye. It is also conjectured that, because fewer dye sites are available (due to the presence of the "neutral"-color dye on the fibers), less dye is required to achieve a deep, uniform color than would be necessary without the solid shade dyeing step.